# Program to find out the similarity between a string and its suffixes in python

Suppose, we are given a string 'input_str'. If we determine all the suffixes from input_str; for example if the string is 'abcd', the suffixes are 'abc', 'bcd', 'cd', 'd'. Now, we check the similarity between input_str and all the suffixes by the length of the longest common prefix in input_str and a suffix. The sum of the similarities between input_str and all the suffixes has to be returned.

So, if the input is like input_str = 'tpotp', then the output will be 7

All the suffixes from the string 'tpotp' are 'tpotp', 'potp', 'otp', 'tp', and 'p'.

If we check the similarity of all the suffixes with input_str, then we get −

'tpotp' similarity 5
'potp' similarity 0
'otp' similarity 0
'tp' similarity 2
'p' similarity 0

Sum of similarities = 5 + 0 + 0 + 2 + 0 = 7.

To solve this, we will follow these steps −

• return_list := a new list containing the size of input_str
• i := 1
• p := 0
• q := 0
• r := 0
• while i < size of input_str, do
• if q < i < (q+p), then
• if return_list[i-q] >= q+p-i, then
• r := q + p - i
• p := 0
• q := 0
• otherwise,
• insert return_list[i-q] at the end of return_list
• i := i + 1
• r := 0
• otherwise,
• while (i + r < size of input_str) and (input_str[r] is same as input_str[i+r]), do
• r := r + 1
• insert r at the end of return_list
• p := r
• q := i
• i := i + 1
• r := 0
• return sum of elements from return_list

## Example

Let us see the following implementation to get better understanding −

def solve(input_str):
return_list = [len(input_str)]
i = 1
p, q = 0,0
r = 0
while i < len(input_str):
if q < i < (q+p):
if return_list[i-q] >= q+p-i:
r = q + p - i
p, q = 0, 0
else:
return_list.append(return_list[i-q])
i += 1
r = 0
else:
while i + r < len(input_str) and input_str[r] == input_str[i+r]:
r += 1
return_list.append(r)
p,q = r,i
i += 1
r = 0
return sum(return_list)

print(solve('tpotp'))

## Input

'tpotp'

## Output

5

Updated on: 11-Oct-2021

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